1. Field of the Invention
The present invention relates to a key switch device, and a method of manufacturing a key switch device.
2. Description of the Related Art
Thin keyboards are desirable for electronic devices such as notebook personal computers or the like, for example. Thus, key switch devices mounted on the keyboard are desired to have low height. For such a purpose, a key switch device including a key top, a pair of gear links having a “V” shape, a membrane sheet switch and a support plate is provided, as disclosed in Patent Documents 1 and 2, for example.
In the key switch device disclosed in Patent Document 1 or 2, the key top fits the gear links by pressing and fitting hooks of the key top and sliding pins of the gear links. However, when inserting the key top, in other words, before fitting the hooks of the key top and the sliding pins of the gear links, the gear links are positioned at a bottom dead center. Thus, it is necessary to attach the key top while pressing a rubber dome of the membrane sheet switch in order to fit the key top and the gear links.
In such a case, when inserting the key top, as the key top first contacts the unstable rubber dome before contacting the gear links that function as a fixing guide, it is hard to align the position of the key top, and as a result, it is hard to insert the key top. Further, as it is hard to align the position of the key top, an operator needs to be skilled in inserting the key top. Thus, the gear links may be damaged by an unskilled operator.
When inserting the key top, it is necessary to match centers of the rubber dome and the gear links while adjusting positions of the rubber dome and the gear links. However, if the position of the key top is shifted in a lateral direction, it is necessary to correct the position of the key top in the lateral direction while fitting the key top to the gear links. At this time, deformation of the rubber dome easily occurs.
If the rubber dome deforms largely, there may be an unusual feeling in a manufactured key switch device such as a click feeling cannot be obtained, or the click feeling is too small in a keying operation. Thus, a problem may be generated such as percent defective is increased, test steps are increased, deficiency when using the key switch device is generated or the like.
Further, measures in order to prevent the deformation of the rubber dome, such as improving the skill of the operator in inserting the key top, or pulling up the key top when inserting the key top or the like, also cause an increase of manufacturing steps and an increase of cost.
Recently, as a demand for thin keyboards for electronic devices is increasing, the size of the rubber dome is becoming small. Thus, the problem of the deformation of the rubber dome happens more often. It is difficult to form the rubber dome with a small size to be capable of retaining the click feeling while retaining the resistance against a force in the lateral direction.
Further, for a key switch device, there is a demand to reduce a keying sound that is generated while operating the key switch device. Conventionally, the key switch device is configured to reduce the sound generated in a keying operation by an elasticity of the rubber dome when it is compressed at a stroke end. However, as the size of the rubber dome becomes small and the stroke is shortened, it is hard to reduce the sound generated in a keying operation because there is not enough space for the compression of the rubber dome.